Testing the new Catapult

I built the new catapult (that I talked about in my last post) and tested it.

Immediately I could see many of the improvements that were expected of the new design:

  • It is easy to adjust.
  • It fires straight.
  • The turntable moves as expected (+/- 30 degrees).
  • The new design is much easier to install on the robot.

However, I found that it was still too inconsistent.  Specifically, the energy stored in the system would gradually decrease as the catapult was used for many shots.  Initially I imagined that the rubber band was stretching and becoming weaker.  But then I realised that the band was slipping along the catapult arm.

So here is the new design for the arm.  It now incorporates a hole for the band to pass through so that it can’t slip along the arm.

Catapult arm (version lost count).

I also found that there was insufficient travel in the trajectory adjuster.  I went for the very high-tech approach of gluing on a piece of Lego to fix that:

Catapult with Lego “tweak”.

This new (dare I say final) version is now yielding much better results.  I’m optimistic it will achieve close to 15 out of 15 shots!

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